What are burnt mounds?

The term burnt mound is applied to a type of prehistoric monument seen all over the British Isles and parts of Western Europe. They are mounds of fire-affected stones, often fractured due to being exposed repeatedly to fire. It is not uncommon for quite a lot of charcoal to be mixed in with the stones, and it is assumed that they are formed by the discarding of stone and fire-waste from a process that is being undertaken, repeatedly, in the vicinity.

Burnt Mound 2 under excavation. The stone slab marks the end of what we believe to be a trough.

Radiocarbon dating of these features tells us that they were formed from the Neolithic period to the Iron Age, with the majority dating from the early Bronze Age (around 2000 BC). Mounds from this period tend to have some characteristics in common, such as evidence for timber or stone-lined troughs, in which water is thought to have been boiled by the heated stones.

What were the heated stones used for? Well archaeologists sometimes disagree over how to interpret features, and in the case of burnt mounds there are very many competing ideas. It has been suggested that the heated stones were used to provide steam for a sweat lodge, like a sauna. Brewing has also been very plausibly proposed, but less likely interpretations, such as tanning and metalworking have also been suggested. It seems safe to assume that water, as well as heated stones, is involved as these mounds are almost always found next to streams. The lakeside situation that we have at Hoppenwood Bank is unusual in being still or relatively slow moving water (www.english-heritage.org.uk/publications/iha-burnt-mounds/burntmounds.pdf). We perhaps should not look at these heaps of burnt stones as representing the result of a single process, they were formed over a very long period of time after all, and could easily represent the remains of a number of processes.

Burnt Mound 1 under excavation. The photograph conveys something of the scale of the accumulation. The timber platform is covered on the left of the photograph.

The dry summer of 2013 substantially lowered the water table, compared to that of the previous two seasons, and this allowed a much more extensive investigation below the dry land margin and into the peat basin itself than we had been able to undertake previously.